This article offers a detailed introduction to the most interesting new features, improvements, and changes visible to users in Thunderbird 91.0. A more comprehensive, but less descriptive list of changes can be found in the Thunderbird 91 Release Notes.

Get Thunderbird in your language! Welcome Latvian!

Thunderbird 91 is available in many different languages from the Thunderbird homepage, translated by the community. Existing installations of Thunderbird will be updated automatically in due time. New: Welcome Latvian as the most recently added language!

Getting started with Thunderbird is easy!

Setting up your existing email address with Thunderbird has never been easier. New: We have polished your onboarding experience and made it easy to connect with your existing online calendars and addressbooks (more below). Account setup now lives in a tab. Just enter your name, email address, and password, and connect instantly!

Simply connect to your existing online address books and calendars: CardDAV and CalDAV support and auto-detection added

Make Thunderbird your Personal Information Manager! Thunderbird ships with integrated calendar, address book and chat modules.

New: Thunderbird now supports remote CardDAV address books and CalDAV calendars. After setting up your existing email address with convenient auto-configuration, Thunderbird will now automatically detect your remote address books and calendars based on the user information you provided.

When adding a Google mail account to Thunderbird, you can easily add your existing Google calendars and address book (see Notes).

Take control of your email experience: Your accounts, your order!

View all of your email accounts in a single, clean, and versatile application. No advertisements, no tracking.

New: Now you can easily change the order in which your accounts will be shown in the Folder Pane:

• Choose ≡ > Account Settings, then drag the main account items into the desired position.
• Alternatively, select a main account item and press Alt + ↓ or Alt + ↑ to change account order via keyboard.

Have your favorite views on email, your way!

Thunderbird lets you choose how you want to view your email messages from several email addresses. New: You can now have several stacked views in your folder pane and arrange them the way you want - just put your favorites first! Here are some of the flavors offered:

• All Folders - View each email account separately with its original folder structure.
• Unified Folders - Combined view on all of your email addresses, with a global inbox, sent folder, etc.
• Favorite Folders - It's your choice! Right-click on any folder, then tick the Favorite Folder context menu item to add a folder to your favorites.

To select the views which you want to pin to your folder pane:

• Choose the Folder Pane Options button ⋯ from the Folder Pane Toolbar, then tick your favorite views. Alternatively, you can use ≡ > View > Folders.
• For ordering your views, unselect all of them and then select those you want in reverse order: Each last selected view becomes your topmost view.
• You can always change your choices or reshuffle them...

Native support for macOS devices built with Apple Silicon

Thunderbird is available for Windows, Linux, and MacOS. New: Native platform support for macOS devices built with Apple Silicon CPUs brings significant performance improvements.

Efficiency where you need it most: Improved addressing area for new messages

Thunderbird has been designed to make your email easier and more efficient. We know that different users have different needs. While we make email easy and accessible for everyone, we also offer enterprise grade efficiency and advanced features. When writing a new message, try these new and improved features in the addressing area:

Privacy and data protection made simple: New public bulk mail notification

New: Thunderbird will now show an inline notification at the bottom of the Write window when you add 15 or more public recipients in the To or Cc address rows. Sending a message to many public recipients may violate their privacy or data protection rights.

• The notification provides a convenient action button, Use Bcc Instead, which will automatically move all public recipients to the Bcc address row to avoid disclosing their email addresses to other recipients.
• You can change the threshold with a hidden preference: mail.compose.warn_public_recipients.threshold

New user interface for adding attachments

• New: Adding attachments with drag and drop is now easier, as you can drop them anywhere on the entire Write window. For images, you can choose whether to insert them inline into your message text or to add them as regular attachments.

• New: The Attachment Pane has been disentangled from the addressing area and relocated to the bottom which maintains visual consistency with how we list attachments when reading a message.

• New: There's a new international keyboard shortcut to access and expand or collapse the non-empty Attachment Pane: Ctrl/Cmd+Shift+M.
• Remember there's also Ctrl/Cmd+Shift+A to add file attachments.
• Did you know that you can reorder your attachments after adding them? With two or more attachments, select one or more attachments for moving, right-click on one of them, and choose any of the actions from the Reorder Attachments panel. You can also sort attachments alphabetically by their file names. For added convenience, the keyboard shortcuts also work when the action panel is closed!

New Remove Text Styling button and updated icons on Formatting Bar

• Improved: There's now a button to remove all text styling from selected text in the Write window. You can use this button to remove text formats like bold, italics, underlined, font color, font size etc. If there is no selection, it will discontinue all text stylings starting from the cursor position. The keyboard shortcut for this command is Ctrl/Cmd+Shift+Y.
• All text formatting icons on the Formatting Bar have been updated to be more distinct and thus easier to remember.

New Redirect action for direct forwarding of a message

New: You can now forward a message as-is, but with the original sender preset in the reply-to address row. This feature can be useful for company-internal or office-internal fast forwards, e.g. from the secretary to the manager. The original message body will remain as-is, but replies to the redirected message will automatically go to the original sender.

• Right-click on a single message in the message list, then choose Redirect from context menu.
• There's also a ↠ Redirect button available from toolbar customization:
  

Right-click on Mail Toolbar, then choose Customize… and drag the button to the desired position on the toolbar.

Convenience without bells and whistles: New integrated PDF viewer

New: Just like Firefox, Thunderbird now features an integrated PDF viewer. So for your convenience, you can just open attached PDF files in a Thunderbird tab without using an external application.

New one-stop print dialog with integrated preview and settings

Improved: Printing has just become better: The new print dialog inherited from the Mozilla platform combines printing, print preview, and print settings in a single, simplified user interface. Or you can still use your system's print dialog if you prefer that.

Themed to please: Choose your colors!

Thunderbird ships with three integrated color themes:

• System theme (default - this will use the colors of your operating system)
• Light theme (on the bright side)
• Dark theme (friendly to your eyes at night)

Try it! You can change your theme with a few clicks, and changes will apply instantly:

≡ > Addons and Themes > Themes, then choose Enable for the theme of your choice.

Improved: Lots of improvements and fixes to the Dark theme, which now applies to almost every part of the application.

Control the density of Thunderbird's user interface

New: The density of Thunderbird's user interface can now be controlled with three modes with decreasing density: Compact, Normal, Touch. Good news for those working on touch enabled devices!

≡ > View > Density > Compact | Normal | Touch

Options renamed to Preferences under Windows for cross-OS consistency

Thunderbird works great on many platforms: Windows, Linux, and MacOS. For Thunderbird on Windows, we have renamed the Options menu to Preferences, so the menu path for configuring Thunderbird is now the same on all platforms:

≡ > Preferences

OpenPGP: Sending encrypted messages to Bcc recipients now possible with a caveat

Improved: You can now send OpenPGP-encrypted messages to Bcc recipients. Thunderbird will show a warning notification that this will indirectly expose your Bcc recipients. For certain scenarios like sending a blind copy of the message to yourself, the risk of exposure might be acceptable.

OpenPGP: New actions for copying key IDs and fingerprints

Thunderbird ships with an integrated OpenPGP key manager for all of your keys. New: Actions for copying key IDs and fingerprints have been added to the context menu of keys.

• ≡ > Tools > OpenPGP Key Manager
• Right-click on an existing key > Copy
• From the Copy submenu, choose between Fingerprint, Key ID and Public Key.

OpenPGP: New Advanced Settings

Thunderbird offers inbuilt encryption using OpenPGP or S/MIME. New: Now you can finetune the behaviour of encryption with three advanced settings which have been added or exposed. We respect that different users have different needs. If encryption is not set up, the advanced settings are not used and therefore disabled. Some of these settings should be used with caution to prevent compromising your privacy.

≡ > Account Settings > Your Account > End-To-End Encryption > Advanced Settings

Calendar: New per-calendar and global notification settings

New: In addition to reminder alerts, you can now set up less intrusive popup notifications for each calendar and globally.

• Right-click on a calendar in the Calendar Pane, then choose Properties.
• Click on ＋ Add Notification button and specify the notification details.
• Confirm the Properties dialog with the OK button.
• Alternatively, you can use the dialog's Global Notification Preferences… button to define notifications for all calendars.

Calendar and Tasks: Undo and Redo support added for events and tasks

New: After creating or deleting tasks or events, you can now undo or redo these actions.

• Ctrl/Cmd + Z: Undo
• Ctrl/Cmd + Y: Redo

Chat: Default server for new chat accounts changed to libera.chat

New: We are happy to offer libera.chat as the new default server for new chat accounts. Formed recently by the former freenode staff team, they provide a welcoming community platform for free and open-source software as well as peer-directed projects. Libera Chat is free and driven by volunteers from all over the world. Let's chat!

Chat: Image-based emoticons replaced with Unicode characters

Improved: When you're expressing yourself with emoticons, Thunderbird is now using generic Unicode characters instead of small images. Simply better!

Chat: Fixes and improvements under the hood

Fixed: A number of small issues have been fixed, and we've made some significant changes under the hood for you to have a smooth chat experience.

• System message collapsing works again, so you can focus on your conversation without noise.
• Chat account settings will now be saved correctly.

FileLink: WeTransfer support removed, but you can still send large attachments through the cloud

Many email servers do not accept messages with large file attachments. With Thunderbird's FileLink feature, you can upload large attachments to the cloud and send a link instead of attaching them directly to your email message. Thunderbird continues to offer support for several other providers via FileLink provider add-ons. To use this feature, you need to install one of these add-ons first:

• ≡ > Preferences > Composition > Attachments > Find more providers...
• Choose a FileLink Provider add-on, and click ＋ Add to Thunderbird.
• Confirm add-on permissions from the popup panel with Add.
• In the Attachments section of the Preferences (see above), click on Add [Your FileLink provider].
• Add information as requested by the addon.
• Thunderbird will suggest using FileLink for attachments larger than 5 MB (you can change the threshold in the same section), or you can right-click on a regular attachment to convert it.

Removed support for movemail

Support for movemail has been removed. Please set up an IMAP or POP3 account to access your email instead.

≡ > New > Existing Mail Account